If breast cancer is detected early, it is very responsive to treatment—but the choice to get screened via mammogram is an area of heated debate. Different governing bodies offer conflicting guidelines on when and how often to get a mammogram. In part I of our two-part series on mammography’s effectiveness, Dr. Mette Kalagar explains the impact of overdiagnosis. Dr. Anthony Miller discusses findings from his large randomized control screening trial, which followed almost 90,000 women for 25 years.